
public class LeetCode_221 {
  class Solution {
    public int maximalSquare(char[][] matrix) {
      int maxSide = 0;
      if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
        return maxSide;
      }
      int rows = matrix.length, columns = matrix[0].length;
      int[][] dp = new int[rows][columns];
      for (int i = 0; i < rows; i++) {
        for (int j = 0; j < columns; j++) {
          if (matrix[i][j] == '1') {
            if (i == 0 || j == 0) {
              dp[i][j] = 1;
            } else {
              dp[i][j] = Math.min(Math.min(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1]) + 1;
            }
            maxSide = Math.max(maxSide, dp[i][j]);
          }
        }
      }
      int maxSquare = maxSide * maxSide;
      return maxSquare;
    }
  }
}
